JP2018082193A - Manufacturing method of permanent magnet material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a permanent magnet material.SOLUTION: A manufacturing method is for plating a front surface of a sintered magnet with a heavy rare earth metal by accepting an ion liquid plating processing, and forming a magnet with a plating layer. The sintered magnet has a thickness of 10 mm or less in at least one direction. In the ion liquid plating processing, plating liquid includes: ion liquid, heavy rare earth salt, VIII group metal salt, alkali metal salt, and an additive agent. A positive electrode is the heavy rare earth metal or heavy rare earth alloy. A negative electrode is the sintered magnet. A plating temperature is in a range of 20 to 50°C. A plating time is in a range of 15 to 80 mins. The manufacturing method can improve a magnet intrinsic coercive force at a low cost, manufacturing efficiency, and availability of heavy rare earth.SELECTED DRAWING: None

Description

  The present invention relates to a method for manufacturing a permanent magnet material, and more particularly to a method for manufacturing a permanent magnet material using an ionic liquid plating process.

  With the increasing emphasis on reducing energy consumption all over the world, energy conservation and exhaust gas reduction have become the most notable issues in each country. Compared to non-permanent magnet motors, permanent magnet motors can improve the energy efficiency ratio. Therefore, in order to reduce energy consumption, motors are manufactured using neodymium-iron-boron (Nd-Fe-B) permanent magnet materials in the fields of air conditioner compressors, electric vehicles, hybrid vehicles, and the like. Since the operating temperature of these motors is relatively high, the magnet is required to have a relatively high intrinsic coercivity (Hcj). It is also required that the magnet has a relatively high magnetic energy product (BH) in order to increase the magnetic flux density of the motor.

  In the conventional neodymium-iron-boron manufacturing process, it is difficult to satisfy the requirements of high magnetic energy product and high intrinsic coercivity. Even if such a requirement is achieved, it is necessary to use a large amount of heavy rare earth metal. Since the world's reserves of heavy rare earth metals are limited, the use of large amounts increases the price of magnets and accelerates the depletion of heavy rare earth resources.

  In order to improve the performance of permanent magnet materials and reduce the amount of heavy rare earths used, various approaches have been made in the industry. Improving the grain boundary by diffusion penetration is an important development direction, and surface coating methods, metal vapor methods, vapor deposition methods, electrodeposition methods, etc. have been developed one after another.

  Patent Document 1 includes 12 to 17 atomic percent rare earth, 3 to 15 atomic percent B, 0.01 to 11 atomic percent metal element, 0.1 to 4 atomic percent O, 0.05 to 3 atomic percent C, and 0.01 to 1 Providing a sintered magnet body consisting of atomic% N and the balance Fe, disposing a powder containing another rare earth oxide, fluoride and / or oxyfluoride on the surface of the magnet body; and A method for producing a rare earth permanent magnet, comprising: heat treating the magnet body coated with the powder in a vacuum or an inert atmosphere at a temperature equal to or lower than a sintering temperature to occlude another kind of rare earth in the sintered magnet body. Is disclosed. However, this method introduces substances that are harmful to the magnets such as O and F, and a lot of scale-like substances are generated on the surface of the infiltrated magnet, and it is necessary to grind the waste of heavy rare earth metals. Bring. According to Patent Document 2, the Nd—Fe—B-based sintered magnet and Dy are arranged at intervals in the processing chamber. Then, under reduced pressure, the processing chamber is heated to raise the temperature of the sintered magnet to a predetermined temperature, while Dy is evaporated, and the evaporated Dy atoms are supplied to the surface of the sintered magnet to be attached. At that time, by controlling the supply amount of Dy atoms to the sintered magnet, a method of manufacturing a permanent magnet that uniformly diffuses Dy into the grain boundary phase of the sintered magnet before forming the Dy layer on the surface of the sintered magnet Is disclosed. This method has the disadvantage that the cost of the equipment is expensive and the evaporation efficiency is low, and the effect of increasing Hcj is not significant.

  Electrodeposition is another important method for forming a rare earth metal thin film on the surface of a magnet. Ionic liquids have low vapor pressure, good stability, good electrical conductivity, characteristics such as design, and specific solubility in many inorganic and organic salts. Currently, ionic liquids are mainly applied to the formation of corrosion-resistant coatings by aluminizing or galvanizing the magnet surface. However, there are few reports that the ionic liquid improves magnetic properties by plating heavy rare earth metal on the surface of the sintered magnet. The reason for this is that it is very difficult to select an appropriate and inexpensive ionic liquid to sufficiently dissolve the heavy rare earth salt and to plate the magnet surface under appropriate plating conditions. Both Patent Document 3 and Patent Document 4 disclose a plating electrodeposition method using tetrafluoroborate, bis (trifluoromethylsulfonyl) imide salt, and bisfluorosulfonylimide salt as an ionic liquid. The ionic liquid is relatively stable in the atmosphere, but its solubility in inorganic metal salts is limited and expensive, so application to plating of magnets for the purpose of improving magnetic properties is This will greatly increase the magnet production cost. Therefore, there is a need for a method for reducing the production cost, significantly improving the intrinsic coercive force, and improving the magnetic properties of neodymium-iron-boron magnets having a relatively high magnetic energy product.

CN101404195 A CN101506919 A CN105839152 A CN105648487 A

  An object of the present invention is to provide a method for producing a permanent magnet material that significantly improves the intrinsic coercivity of a neodymium-iron-boron magnet at a low production cost. Another object of the present invention is to provide a method for producing a permanent magnet material in which the resulting magnet has a relatively high magnetic energy product. A further object of the present invention is to provide a method for producing a permanent magnet material that has a high utilization rate of heavy rare earth metal, high production efficiency, mild production conditions, and suitable for industrial production.

  The present invention provides a method for producing a permanent magnet material including the following steps.

R-Fe-BM type sintered magnet (R is one or more kinds of Nd, Pr, Dy, Tb, Ho, Gd, and the R content is 24wt% to 35wt% of the total weight of the sintered magnet. And M is one or more selected from Ti, V, Cr, Mn, Co, Ni, Ga, Ca, Cu, Zn, Si, Al, Mg, Zr, Nb, Hf, Ta, W, Mo. The content of M is 0 to 5 wt% of the total weight of the sintered magnet, the content of B is 0.5 wt% to 1.5 wt% of the total weight of the sintered magnet, and the balance is Fe. Magnet manufacturing process S1), which manufactures
An ionic liquid plating process for forming a magnet with a plating layer by plating heavy rare earth metal on the surface of the sintered magnet by an ionic liquid plating process, wherein the sintered magnet has a thickness of 10 mm or less in at least one direction In the ionic liquid plating process, the plating solution contains an ionic liquid, a heavy rare earth salt, a Group VIII metal salt, an alkali metal salt, and an additive, the anode is a heavy rare earth metal or a heavy rare earth alloy, and the cathode is the aforementioned Sintered magnet, plating temperature is 20-50 ° C, plating time is 15-80min, ionic liquid plating step S2),
Heat treating the magnet with the plated layer, and diffusing heavy rare earth metal into the sintered magnet, diffusion step S3), and
An aging treatment step S4) for aging treatment of the magnet obtained from the diffusion step S3).

（ここで、R₁とR₂は、それぞれ独立してC1〜C8アルキルから選ばれるものであり、Xは、Cl^-、CF₃SO₃ ^-またはN（CN）₂ ^-から選ばれるものである。） Here, the ionic liquid is a compound having the following structure.

(Where R ₁ and R ₂ are each independently selected from C1-C8 alkyl, and X is selected from Cl ⁻ , CF ₃ SO ₃ ^— or N (CN) ₂ ^— ) .)

  The additive is selected from ethylene glycol, urea, aromatic compounds, or alkyl halides.

According to the method of the present invention, preferably, R ₁ and R ₂ are each independently selected from C1-C4 alkyl, and X is selected from CF ₃ SO ₃ ^— or N (CN) ₂ ^—. It is what

  According to the method of the present invention, preferably, the ionic liquid is 1-butyl-3-methylimidazolium chloride, 1-butyl-3-ethylimidazolium chloride, 1,3-bismethylimidazolium chloride, 1-butyl chloride. Hexyl-3-methylimidazolium, 1-octyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-ethylimidazolium trifluoromethanesulfonate, 1 , 3-Bismethylimidazolium trifluoromethanesulfonate, 1-hexyl-3-methylimidazolium trifluoromethanesulfonate, 1-octyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methyl Imidazolium dicyandiamide salt, 1-butyl-3-ethylimidazolium dicyandiamide salt, 1,3-bismethylimidazolium di Cyandiamide salt, 1-hexyl-3-methylimidazolium dicyandiamide salt or 1-octyl-3-methylimidazolium dicyandiamide salt is selected.

According to the method of the present invention, preferably, in the plating solution, the heavy rare earth element of the heavy rare earth salt is selected from Gd, Tb, Dy or Ho, and the Group VIII metal of the Group VIII metal salt is Fe. , Selected from Co or Ni, the alkali metal of the alkali metal salt is selected from Li, Na or K, and the additive is an aromatic compound,
In the anode, the heavy rare earth metal is selected from Gd, Tb, Dy, or Ho, and the heavy rare earth alloy is selected from an alloy formed of the heavy rare earth metal and Fe.

According to the method of the present invention, preferably, in the plating solution, the heavy rare earth salt is a heavy rare earth element chloride, nitrate or sulfate, and the group VIII metal salt is a group VIII metal chloride, The alkali metal salt is an alkali metal chloride, and the aromatic compound is one or more of benzene, toluene, xylene, and ethylbenzene,
In the anode, the heavy rare earth metal is Tb, and the heavy rare earth alloy is an alloy formed of Tb and Fe.

  According to the method of the present invention, the ratio of the total amount of the heavy rare earth salt and the group VIII metal salt to the amount of the ionic liquid is 0.25 to 3: 1, and the amount of the heavy rare earth salt And the amount of the group VIII metal salt is 0.25 to 10: 1, and in the plating solution, the concentration of the alkali metal salt is 10 to 200 g / L, and the additive and the ionic liquid The volume ratio is preferably 10 vol% to 400 vol%.

  According to the method of the present invention, the ionic liquid plating step S2) is preferably performed by any of the following methods under anhydrous oxygen-free conditions.

(1) Constant current plating with a current density of 5-20 mA / cm ²
(2) Pulse voltage plating with an average pulse voltage of 5-8V, a duty ratio of 20% -50%, and a pulse frequency of 2-5kHz.

  According to the method of the present invention, preferably, the method further comprises mixing the heavy rare earth salt, the group VIII metal salt and the ionic liquid uniformly at a temperature of 80 ° C. or lower under anhydrous oxygen-free conditions to obtain an alkali metal salt. And the additive are added and mixed uniformly to obtain the plating solution.

  According to the method of the present invention, preferably, in the diffusion step S3), the heat treatment temperature is 850 to 1000 ° C., the heat treatment time is 3 to 8 hours, and in the aging treatment step S4), the treatment temperature is 400 ˜650 ° C. and the treatment time is 2 to 5 hours.

  According to the method of the present invention, preferably, the magnet manufacturing step S1) includes the following steps.

Smelting process S1-1) to smelt magnet raw material and form an alloy sheet with a thickness of 0.01-2mm,
The alloy sheet is subjected to hydrogen storage / release treatment in a hydrogen cracking furnace to form a magnetic coarse powder having an average particle size D50 of 200 to 350 μm, and then the magnetic coarse powder is subjected to an average particle size D50 by a jet mill. A milling step S1-2) for crushing into magnetic fine powder of 2 to 20 μm,
A molding step S1-3) in which the magnetic fine powder is pressed into a green body by the action of an orientation magnetic field; and
Sintering / cutting step in which the green body is sintered at a sintering temperature of 960 to 1100 ° C. and then shaped, and then cut into a sintered magnet, wherein the sintered magnet has an oxygen content of less than 2000 ppm -Cutting process S1-4).

  In the production method of the present invention, the ionic liquid used has good solubility in inorganic metal salts, is cheaper, and the heavy rare earth metal is applied to the surface of the neodymium-iron-boron magnet by controlling the process conditions. Permanent magnet that has excellent intrinsic coercive force and magnetic energy product by depositing, melting heavy rare earth metal by heat treatment, diffusing to the grain boundary phase inside neodymium-iron-boron magnet, and adopting aging treatment A material is obtained. The production method of the present invention is applied to industrial production with high production efficiency, high utilization rate of heavy rare earths, mild production conditions.

  Hereinafter, the present invention will be described in detail based on embodiments, but the content of the present invention is not limited thereto.

  The “average particle size D50” according to the present invention represents the maximum value of the equivalent diameter of particles when the cumulative distribution is 50% in the particle size distribution curve.

  The “vacuum” according to the present invention is an absolute vacuum. It shows that a vacuum degree becomes high, so that the value of the absolute vacuum degree is small.

  The production method of the present invention includes a magnet production step S1), an ionic liquid plating step S2), a diffusion step S3), and an aging treatment step S4). Each will be described next.

<Magnet manufacturing process>
The magnet manufacturing step S1) of the present invention can include the following specific steps.

Smelting process S1-1) to smelt magnet raw material and form an alloy sheet with a thickness of 0.01-2mm,
The alloy sheet is subjected to hydrogen storage / release treatment to form a magnetic coarse powder having an average particle size D50 of 200 to 350 μm, and then the magnetic coarse powder is obtained by jet milling with an average particle size D50 of 2 to 20 μm. A milling step S1-2) to break up into a magnetic fine powder
A molding step S1-3) in which the magnetic fine powder is pressed into a green body by the action of an orientation magnetic field; and
The green body is sintered and shaped at a sintering temperature of 960 to 1100 ° C., and then cut into a sintered magnet, and the sintered magnet has an oxygen content of less than 2000 ppm. Cutting step S1-4).

  In the smelting step S1-1) of the present invention, the magnet raw material contains R, Fe, B and M. R is one or more selected from Nd, Pr, Dy, Tb, Ho, Gd, preferably R is selected from Nd, Pr, or Dy, and more preferably R is Nd. The content of R is 24 wt% to 35 wt% of the total weight of the sintered magnet, preferably the content is 25 wt% to 33 wt%, more preferably 28 wt% to 32 wt%. M is one or more selected from Ti, V, Cr, Mn, Co, Ni, Ga, Ca, Cu, Zn, Si, Al, Mg, Zr, Nb, Hf, Ta, W, Mo, Preferably, it is one or more selected from Mn, Co, Ni, Ga, Ca, Cu, Zn, Al, and Zr. The M content is 0 to 5 wt%, preferably 0.05 wt% to 3 wt% of the total weight of the sintered magnet. The content of B is 0.5 wt% to 1.5 wt%, preferably 0.5 wt% to 1 wt% of the total weight of the sintered magnet. The balance of the magnet raw material is Fe.

The smelting step S1-1) of the present invention is performed in a vacuum or in an inert atmosphere in order to avoid oxidation of a magnet raw material (eg, neodymium-iron-boron magnet raw material) and an alloy sheet obtained from the magnet raw material. . The smelting process may be an ingot casting process or a strip casting process. The ingot casting process is a process for producing an alloy ingot by cooling and solidifying a smelted magnet raw material. The strip casting process is a process in which a smelted magnet raw material is rapidly cooled and solidified, and produced into an alloy sheet. For example, for neodymium-iron-boron magnet raw material, compared to the ingot casting process, the strip casting process can avoid the generation of α-Fe, which affects the uniformity of magnetic powder, and the nodular neodymium rich Since the generation of the phase can be avoided, it is advantageous for refining the crystal grain size of the main phase Nd ₂ Fe ₁₄ B. Therefore, the smelting process of the present invention is preferably a strip cast process. The strip casting process is usually performed in a vacuum rapid solidification induction furnace. The thickness of the alloy sheet of the present invention may be from 0.01 to 2 mm, preferably from 0.05 to 1 mm, more preferably from 0.2 to 0.35 mm.

The milling step S1-2) of the present invention is performed in a vacuum or in an inert atmosphere in order to avoid oxidation of the alloy sheet and the magnetic powder. The alloy sheet is subjected to hydrogen storage / release treatment in a hydrogen crushing furnace to form a magnetic coarse powder having an average particle size D50 of 200 to 350 μm. The average particle size D50 of the magnetic coarse powder is preferably 230 to 300 μm. In the hydrogen crushing process, first, the alloy sheet is occluded with hydrogen, and the reaction between the alloy sheet and hydrogen gas causes volume expansion of the lattice of the alloy sheet to crush the alloy sheet to form a magnetic coarse powder. Heating the magnetic coarse powder to release hydrogen. According to a preferred embodiment of the present invention, in the hydrogen cracking process of the present invention, the hydrogen storage temperature is 20 ° C. to 400 ° C., preferably 100 ° C. to 300 ° C., and the hydrogen storage pressure is 50 to 600 kPa. Yes, preferably 100 to 500 kPa, and the hydrogen release temperature is 400 to 1000 ° C, preferably 500 to 600 ° C. The magnetic coarse powder is pulverized into fine magnetic powder having an average particle size D50 of 2 to 20 μm by a jet mill process. The magnetic fine powder preferably has an average particle size D50 of 3 to 10 μm. In the jet mill process, magnetic coarse powder is accelerated using an air flow and collides with each other to be crushed. The air stream may be a nitrogen gas stream, preferably a high purity nitrogen gas stream. The N ₂ content in the high purity nitrogen gas stream may be 99.0 wt% or more, preferably 99.9 wt% or more. The pressure of the airflow may be 0.1 to 2.0 MPa, preferably 0.5 to 1.0 MPa, and more preferably 0.6 to 0.7 MPa.

The forming step S1-3) of the present invention is performed in a vacuum or an inert atmosphere in order to avoid oxidation of the magnetic powder. The magnetic powder pressing process can employ a mold pressing process and / or an isotropic pressure pressing process. As the mold pressing process and the isotropic pressure pressing process, those known in the industry can be adopted, and the description thereof is omitted here. The magnetic fine powder is pressed by the action of an orientation magnetic field to form a green body. The orientation magnetic field direction and the magnetic powder pressing direction are oriented parallel to each other or perpendicular to each other. According to one embodiment of the present invention, the strength of the orientation magnetic field is 1-5 Tesla (T), preferably 1.5-3T, more preferably 1.6-1.8T. The density of the green body from the molding step S1-3) of the may be ^{3.5g / cm 3 ~5.0g / cm 3} , preferably from ^{3.8g / cm 3 ~4.4g / cm 3} .

In order to avoid oxidation of the green body, the sintering process of the sintering and cutting step S1-4) of the present invention is also performed in a vacuum or an inert atmosphere. The sintering process can be performed in a vacuum sintering furnace. The sintering temperature may be 960-1100 ° C, preferably 1050-10060 ° C. The sintering time may be 3 to 10 hours, preferably 5 to 6 hours. The density of the sintered magnet obtained from the sintering process may be ^{6.5g / cm 3 ~8.9g / cm 3} , preferably from ^{7.3g / cm 3 ~7.9g / cm 3} . The oxygen content is preferably less than 2000 ppm and most preferably less than 1200 ppm. The sintered green body obtained from the sintering process can be cut by a slicing process and / or a wire discharge cut process and / or a diamond wire cut process. The sintered green body is cut into sintered magnets having a thickness in at least one direction of 10 mm or less, preferably 4 mm or less, preferably the thickness is 10 mm or less, preferably 4 mm or less is the orientation direction of the sintered magnet is not.

  By the above process, an R—Fe—B—M type sintered magnet (the definitions of R, Fe, B and M are the same as those described above, and are omitted here).

<Ionic liquid plating process>
In the ionic liquid plating step S2) of the present invention, a heavy rare earth metal is plated on the surface of the sintered magnet by an ionic liquid plating process to form a magnet with a plating layer. The sintered magnet has a thickness of 10 mm or less in at least one direction. Preferably, the direction in which the thickness is 10 mm or less is not the orientation direction of the sintered magnet.

  In the ionic liquid plating process of the present invention, a solution containing an ionic liquid, a heavy rare earth salt, a Group VIII metal salt, an alkali metal salt and an additive is used as a plating solution, and a heavy rare earth metal or heavy rare earth alloy is used as an anode. Is the cathode. The inventors can significantly improve the plating effect by controlling the plating temperature to 20 to 50 ° C., preferably 30 to 35 ° C., and the plating time to 15 to 80 min, preferably 30 to 60 min. It has been discovered that a simple ionic liquid can improve the intrinsic coercivity and magnetic energy product of a magnet. In the present invention, since the plating conditions are mild and the plating time is appropriate, the production efficiency can be improved.

  In the present invention, the ionic liquid is always stored in an anhydrous and oxygen-free atmosphere in order to avoid destruction of the plating solution due to residual moisture and oxygen or changes in the electrochemical inlet of the plating solution.

そのうち、R₁とR₂は、それぞれ独立してC1〜C8アルキルから選ばれるものであり、Xは、Cl^-、CF₃SO₃ ^-またはN（CN）₂ ^-から選ばれるものである。好ましくは、R₁とR₂がそれぞれ独立してC1〜C4アルキルから選ばれるものであり、Xは、CF₃SO₃ ^-またはN（CN）₂ ^-から選ばれるものである。R₁とR₂の実例として、メチル、エチル、プロピル、プチル、ペンチル基、ヘキシル基、ヘプチル基およびオクチル基等が挙げられるが、これらに限定されるものではない。好ましくは，前記イオン液体は、塩化1-ブチル-3-メチルイミダゾリウム、塩化1-ブチル-3-エチルイミダゾリウム、塩化1、3-ビスメチルイミダゾリウム、塩化1-ヘキシル-3-メチルイミダゾリウム、塩化1-オクチル-3-メチルイミダゾリウム、1-ブチル-3-メチルイミダゾリウムトリフルオロメタンスルホン酸塩、1-ブチル-3-エチルイミダゾリウムトリフルオロメタンスルホン酸塩、1,3-ビスメチルイミダゾリウムトリフルオロメタンスルホン酸塩、1-ヘキシル-3-メチルイミダゾリウムトリフルオロメタンスルホン酸塩、1-オクチル-3-メチルイミダゾリウムトリフルオロメタンスルホン酸塩、1-ブチル-3-メチルイミダゾリウムジシアンジアミド塩、1-ブチル-3-エチルイミダゾリウムジシアンジアミド塩、1,3-ビスメチルイミダゾリウムジシアンジアミド塩、1-ヘキシル-3-メチルイミダゾリウムジシアンジアミド塩または1-オクチル-3-メチルイミダゾリウムジシアンジアミド塩から選ばれるものである。より好ましくは、前記イオン液体は、塩化1-ブチル-3-メチルイミダゾリウム、塩化1-ブチル-3-エチルイミダゾリウム、1-ブチル-3-メチルイミダゾリウムトリフルオロメタンスルホン酸塩、1-ブチル-3-エチルイミダゾリウムトリフルオロメタンスルホン酸塩、1-ブチル-3-メチルイミダゾリウムジシアンジアミド塩、1-ブチル-3-エチルイミダゾリウムジシアンジアミド塩、1,3-ビスメチルイミダゾリウムジシアンジアミド塩、1-ヘキシル-3-メチルイミダゾリウムジシアンジアミド塩または1-オクチル-3-メチルイミダゾリウムジシアンジアミド塩から選ばれるものである。本発明の一つの実施形態によれば、前記イオン液体は、塩化1-ブチル-3-メチルイミダゾリウムまたは1-ブチル-3-メチルイミダゾリウムトリフルオロメタンスルホン酸塩である。 The ionic liquid of the present invention is a compound having the following constitution.

Among them, R ₁ and R ₂ are each independently selected from C ₁ -C 8 alkyl, and X is selected from Cl ⁻ , CF ₃ SO ₃ ^— or N (CN) ₂ ^— . Preferably, R ₁ and R ₂ are each independently selected from C ₁ -C 4 alkyl, and X is selected from CF ₃ SO ₃ ^— or N (CN) ₂ ^— . Illustrative examples of R ₁ and R ₂ include, but are not limited to, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl and octyl. Preferably, the ionic liquid is 1-butyl-3-methylimidazolium chloride, 1-butyl-3-ethylimidazolium chloride, 1,3-bismethylimidazolium chloride, 1-hexyl-3-methylimidazolium chloride 1-octyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-ethylimidazolium trifluoromethanesulfonate, 1,3-bismethylimidazolium Trifluoromethanesulfonate, 1-hexyl-3-methylimidazolium trifluoromethanesulfonate, 1-octyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium dicyandiamide salt, 1- Butyl-3-ethylimidazolium dicyandiamide salt, 1,3-bismethylimidazolium dicyandiamide salt, 1-he Sill-3 are those selected from methyl imidazolium dicyandiamide salt or 1-octyl-3-methylimidazolium dicyandiamide salt. More preferably, the ionic liquid is 1-butyl-3-methylimidazolium chloride, 1-butyl-3-ethylimidazolium chloride, 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl- 3-ethylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium dicyandiamide salt, 1-butyl-3-ethylimidazolium dicyandiamide salt, 1,3-bismethylimidazolium dicyandiamide salt, 1-hexyl- It is selected from 3-methylimidazolium dicyandiamide salt or 1-octyl-3-methylimidazolium dicyandiamide salt. According to one embodiment of the invention, the ionic liquid is 1-butyl-3-methylimidazolium chloride or 1-butyl-3-methylimidazolium trifluoromethanesulfonate.

  Compared to ionic liquids such as tetrafluoroborate, bis (trifluoromethanesulfonyl) imide salt and bisfluorosulfonylimide salt, the present inventors have good solubility in the inorganic metal salt of the ionic liquid of the present invention, In addition, it was surprisingly discovered that a heavy rare earth metal thin film can be plated on a magnet surface in a relatively short time under relatively mild conditions while being relatively inexpensive, and further, the intrinsic coercivity of the magnet is improved.

  In the plating solution of the present invention, the heavy rare earth salt is a chloride, nitrate or sulfate of a heavy rare earth element. The heavy rare earth element of the heavy rare earth salt may be selected from Gd, Tb, Dy or Ho, and is preferably Tb or Dy. Examples of heavy rare earth salts include, but are not limited to, dysprosium chloride, terbium chloride, dysprosium nitrate, terbium nitrate, and the like.

  In the plating solution of the present invention, the Group VIII metal salt may be a Group VIII metal chloride. The Group VIII metal of the Group VIII metal salt may be selected from Fe, Co, or Ni, preferably Fe or Ni. Illustrative examples of Group VIII metal salts include, but are not limited to, iron chloride, cobalt chloride or nickel chloride.

  In the plating solution of the present invention, the alkali metal salt may be an alkali metal chloride. The alkali metal of the alkali metal salt may be selected from Li, Na or K, preferably Na or K. Examples of alkali metal salts include, but are not limited to, sodium chloride and potassium chloride.

  The plating solution of the present invention further contains an additive. The additive is selected from ethylene glycol (EG), urea, aromatic compounds or alkyl halides, preferably aromatic compounds. The aromatic compound may be selected from one or more of benzene, toluene, xylene, and ethylbenzene, and is preferably benzene or toluene. Illustrative examples of alkyl halides include, but are not limited to, methyl chloride, methylene chloride, or chloroform. In the present invention, the solubility of the ionic liquid, the viscosity, and the conductive performance can be improved by the addition of the additive, particularly the aromatic compound, so that the plating time is shortened and the production efficiency is improved.

  In the plating solution of the present invention, the ratio of the total amount (unit: mol) of the heavy rare earth salt and the group VIII metal salt to the amount of the ionic liquid (unit: mol) is 0.25-3: 1. And preferably 0.5-2: 1. The ratio of the amount of heavy rare earth salt (unit: mole) to the amount of group VIII metal salt (unit: mole) is 0.25 to 10: 1, preferably 0.5 to 9: 1. Based on the plating solution, the concentration of the alkali metal salt is 10 to 200 g / L, preferably 30 to 60 g / L. The volume ratio of the additive to the ionic liquid may be 10 vol% to 400 vol%, preferably 30 vol% to 50 vol%. By controlling the parameter within the above range, the plating effect can be further improved, and the intrinsic coercivity and magnetic energy product of the magnet can be improved.

  In the anode of the present invention, the heavy rare earth metal may be selected from Gd, Tb, Dy or Ho, preferably Tb or Dy. The heavy rare earth alloy may be selected from an alloy formed of the heavy rare earth metal and Fe. The cathode of the present invention is a sintered magnet to be plated obtained in the magnet manufacturing step S1), and since this is described in the preamble, description thereof is omitted here.

In order to improve the plating effect, the ionic liquid plating step S2) is most preferably performed under anhydrous oxygen-free conditions. The ionic liquid plating step S2) may employ constant current plating, and the current density is 5 to 20 mA / cm ² , preferably 10 to 16 mA / cm ² . The ionic liquid plating step S2) may adopt pulse voltage plating, the pulse voltage average value is 5 to 8 V, the duty ratio is 20% to 50%, and the pulse frequency is 2 to 5 kHz. According to one embodiment of the present invention, the pulse voltage average value is 6-8V, the duty ratio is 30% -50%, and the pulse frequency is 3-5 kHz. The plating temperature of the present invention is the temperature of the ionic liquid, and may be 20 to 50 ° C., preferably 30 to 35 ° C. In order to avoid destruction of the plating solution, the entire plating tank can be sealed with a glove box and a protective gas (for example, nitrogen gas or argon gas) can be ventilated.

  In order to improve the plating effect, the ionic liquid plating step S2) of the present invention may include a pretreatment step of a sintered magnet to be plated, a posttreatment step of a sintered magnet after plating, and the like. For example, the process of cleaning and activating the surface of a sintered magnet by a process such as deoiling → rust removal → activation → drying, and magnet after plating using a solvent such as absolute ethanol, acetone, alkyl halide, benzene A step of cleaning the surface is mentioned. Since these steps are all well known in the art, description thereof will be omitted.

<Diffusion process>
The diffusion step S3) of the present invention is a step of diffusing heavy rare earth metal into the sintered magnet by heat-treating the magnet with plating layer. The diffusion of the present invention includes a process in which heavy rare earth metal penetrates from the magnet surface to the inside of the magnet, and further includes a diffusion process inside the heavy rare earth metal magnet. The heavy rare earth metal deposited on the surface of the sintered magnet by heat treatment is immersed in the grain boundary phase in the sintered magnet. The heat treatment temperature may be 850-1000 ° C, preferably 900-950 ° C. The heat treatment time is 3 to 8 hours, preferably 3.5 to 5 hours. By controlling the heat treatment temperature and time within the above ranges, the intrinsic coercive force and magnetic energy product of the sintered magnet can be further improved.

  The diffusion step S3) of the present invention is performed in a vacuum or an inert atmosphere. This avoids oxidation of the sintered magnet surface during the heat treatment process. The oxidized magnet surface can prevent further penetration of heavy rare earth elements. The absolute vacuum degree in the diffusion step S3) may be 0.000001 to 0.1 Pa, preferably 0.00001 to 0.01 Pa.

<Aging process>
The aging treatment step S4) of the present invention is a step of aging treatment of the magnet obtained from the diffusion step S3). The treatment temperature is 400 to 650 ° C, preferably 500 to 550 ° C. The treatment time is 2 to 5 hours, preferably 3 to 5 hours. By controlling the aging treatment temperature and time within the above ranges, the intrinsic coercive force and magnetic energy product of the sintered magnet can be further improved. In order to prevent oxidation of the sintered magnet, the aging treatment step S4) is performed in a vacuum or in an inert atmosphere. The absolute vacuum degree in the aging treatment step S4) may be 0.000001 to 0.1 Pa, preferably 0.00001 to 0.01 Pa.

Example 1-2 and Comparative Example 1
S1) Magnet manufacturing process:
S1-1) Smelting process: Prepare magnet raw material with Nd 23.5%, Pr 5.5%, Dy 2%, B 1%, Co 1%, Cu 0.1%, Zr 0.08%, Ga 0.1% and balance Fe in weight percentage did. The magnet raw material was put into a vacuum smelting rapid solidification furnace and smelted to produce an alloy sheet with an average thickness of 0.3 mm.

  S1-2) Milling step: Hydrogen storage / escape treatment was performed in a hydrogen crushing furnace so that the alloy sheet became D50 300 μm magnetic coarse powder. The magnetic coarse powder was pulverized into a fine magnetic powder having a D50 of 4.2 μm by a jet mill using nitrogen gas as a medium.

S1-3) Molding step: The magnetic fine powder was molded into a green body by applying a 1.8 T orientation magnetic field in a molding press machine protected with nitrogen gas. The density of the green body is 4.3 g / cm ³ .

S1-4) Sintering / cutting step: The green body is put in a vacuum sintering furnace having an absolute vacuum exceeding 0.1 Pa, sintered at 1050 ° C. for 5 hours, and the density is 7.6 g / cm ^3. A magnet having a size of 50 mm × 40 mm × 30 mm was obtained. The magnet was cut into sintered magnets having dimensions of 38 mm × 23.5 mm × 4 mm.

S2) Ionic liquid plating process:
The sintered magnet was subjected to deoiling → rust removal → pickling activation → drying treatment to produce a sintered magnet to be plated.

  Anhydrous terbium chloride, anhydrous cobalt chloride and 1-butyl-3-methylimidazolium chloride with a molar ratio of 1: 0.5: 1 in a glove box protected with nitrogen gas at a temperature of less than 80 ° C ( (Ionic liquid) is stirred uniformly, and sodium chloride with a concentration of 30 g / L (based on the plating solution) is added, and benzene with a volume ratio of 30 vol% to the ionic liquid is added and stirred uniformly to plate. A liquid was formed.

Plating was performed using a constant current method, the entire plating tank was sealed using a glove box, and nitrogen gas was vented. A Tb metal block material is used as an anode, and a sintered magnet to be plated is used as a cathode. The anode current density is 16 mA / cm ² and the temperature of the ionic liquid is 35 ° C. Plate for 10 min (Comparative Example 1), 30 min, and 60 min, respectively. The plated magnet was immediately washed with absolute ethanol and then dried.

  S3) Diffusion process: The magnet with the Tb plating layer obtained from the ionic liquid plating process S2) was heat-treated at 900 ° C. for 5 hours under the condition where the absolute vacuum exceeded 0.01 Pa.

  S4) Aging treatment step: The magnet obtained from the diffusion step S3) was aged at 500 ° C. for 3 hours under the condition that the absolute vacuum exceeded 0.01 Pa. The obtained magnet was cut into magnets having dimensions of 9 mm × 9 mm × 4 mm, and the results were entered in Table 1.

table 1

  As can be seen from Table 1, the plating time of the ionic liquid has an influence on any of the residual magnetic flux density, the maximum magnetic energy product, and the intrinsic coercive force of the magnet. When the plating time exceeds 10 min, the intrinsic coercivity increases as the time increases, whereas when the time increases to some extent, the intrinsic coercivity does not obviously increase.

Example 3-6 and Comparative Example 2
S1) Magnet manufacturing process:
S1-1) Smelting process: Nd 22.3% by weight, Pr 6.4%, Dy 3%, B 1%, Co 2%, Cu 0.2%, Zr 0.08%, Ga 0.15% and the remainder of the magnet raw material Prepared. The magnet raw material was smelted in a vacuum fast coagulator to produce an alloy sheet having an average thickness of 0.3 mm.

  S1-2) Milling step: The alloy sheet is subjected to hydrogen storage / escape treatment in a hydrogen cracking furnace, the alloy sheet is formed into a magnetic coarse powder having a D50 of 300 μm, and the magnetic coarse powder is used as a medium with nitrogen gas. The powder was pulverized to a fine magnetic powder having a D50 of 3.8 μm by a jet mill.

S1-3) Molding step: The magnetic fine powder was pressed into a green body by applying an orientation magnetic field of 1.8 T in a molding press machine protected with nitrogen gas. The density of the green body was 4.3 g / cm ³ .

S1-4) Sintering step: The green body is put in a vacuum sintering furnace with an absolute vacuum exceeding 0.1 Pa, sintered at 1055 ° C. for 5 hours, the density is 7.62 g / cm ³ , and the dimensions are 50 mm × A magnet with a size of 40 mm × 30 mm was obtained. The magnet was cut into sintered magnets having dimensions of 38 mm × 23.5 mm × 2 mm.

S2) Ionic liquid plating process:
The sintered magnet was subjected to deoiling → rust removal → pickling activation → drying treatment to produce a sintered magnet to be plated.

  Anhydrous dysprosium chloride, anhydrous nickel chloride and 1-butyl-3-methylimidazolium trifluoromethanesulfonate at a molar ratio of 1.5: 0.5: 1 in a glove box protected with nitrogen gas at a temperature of less than 80 ° C (Ionic liquid) is stirred uniformly, and potassium chloride with a concentration of 30 g / L (based on the plating solution) is added, and toluene with a volume ratio of 50 vol% to the ionic liquid is added and stirred uniformly. Then, a plating solution was formed.

Plating was performed using a constant current method, the entire plating tank was sealed using a glove box, and nitrogen gas was vented. A Dy metal block material is used as an anode, and a sintered magnet to be plated is used as a cathode. The anode current density was 15 mA / cm ² , the temperature of the ionic liquid was 35 ° C., and plating was performed for 30 min. The plated magnet was immediately washed with toluene, then washed with absolute ethanol and dried.

  S3) Diffusion process: Dy-plated layer magnets obtained from ionic liquid plating process S2) were heat-treated at different temperatures for 5 hours under conditions where the absolute vacuum exceeds 0.01 Pa. The heat treatment temperatures were 850 ° C, 900 ° C and 950 ° C, respectively. ℃ and 1000 ℃.

  S4) Aging treatment step: The magnet obtained from the diffusion step S3) was aged at 510 ° C. for 3 hours under the condition that the absolute vacuum exceeded 0.01 Pa. The obtained magnet was cut into magnets having dimensions of 9 mm × 9 mm × 2 mm, and the results are entered in Table 2.

  For comparison, the aging treatment step S4) is directly performed on the sintered magnet obtained from the magnet manufacturing step S1) without performing the treatment in the ionic liquid plating step S2) and the diffusion step S3), and A magnet having a size of 9 mm × 9 mm × 2 mm was processed and measured to obtain Comparative Example 2. See Table 2 for results.

Table 2

  As can be seen from Table 2, the heat treatment temperature in the diffusion step S2) has an effect on any of the residual magnetic flux density, maximum magnetic energy product, and intrinsic coercivity of the neodymium-iron-boron permanent magnet material. When the heat treatment temperature is relatively low or very high, none of the numerical increase effects of the above parameters are clear.

Example 7-9 and Comparative Example 3
S1) Magnet manufacturing process:
S1-1) Smelting process: By weight percentage, Nd 27.4%, Dy 4.5%, B 0.97%, Co 2%, Cu 0.2%, Zr 0.08%, Ga 0.2%, Al 0.3% and the remainder of the magnet material from Fe Prepared. The magnet raw material was smelted in a vacuum fast coagulator to produce an alloy sheet having an average thickness of 0.3 mm.

  S1-2) Milling step: The alloy sheet is subjected to hydrogen storage / escape treatment in a hydrogen cracking furnace, the alloy sheet is formed into a magnetic coarse powder having a D50 of 300 μm, and the magnetic coarse powder is used as a medium with nitrogen gas. The powder was pulverized to a fine magnetic powder having a D50 of 3.8 μm by a jet mill.

S1-3) Molding step: The magnetic fine powder was pressed into a green compact by applying a 1.8 T orientation magnetic field in a nitrogen gas-protected molding press. The density of the green body is 4.3 g / cm ³ .

S1-4) Sintering and cutting step: The green body is put in a vacuum sintering furnace with an absolute vacuum exceeding 0.1 Pa, sintered at 1055 ° C. for 5 hours, the density is 7.63 g / cm ³ and the dimensions are A magnet having a size of 50 mm × 40 mm × 30 mm was obtained. The magnet was cut into sintered magnets having dimensions of 38 mm × 23.5 mm × 2.2 mm.

S2) Ionic liquid plating process:
The sintered magnet was subjected to deoiling → rust removal → pickling activation → drying treatment to produce a sintered magnet to be plated.

  Anhydrous terbium chloride, anhydrous iron chloride and 1-butyl-3-methylimidazolium trifluoromethanesulfonate with a molar ratio of 1: 1: 1 in a glove box protected with nitrogen gas at a temperature of less than 80 ° C (Ionic liquid) is stirred uniformly, and lithium chloride with a concentration of 40 g / L (based on the plating solution) is added, and toluene with a volume ratio of 30 vol% to the ionic liquid is added and stirred uniformly. Then, a plating solution was formed.

  The pulse voltage plating method is adopted, the glove box is used to seal the entire plating tank, and nitrogen gas is vented. An alloy block material of Tb and Fe having a Tb content of 75% by mass is used as an anode, and the sintered magnet to be plated is used as a cathode. The pulse voltage average value is 7 V, the pulse frequency is 3.0 kHz, the duty ratio is 40%, the ionic liquid temperatures are 20 ° C., 35 ° C. and 50 ° C., respectively, and the plating time is 30 min. Immediately wash the magnet after plating with absolute ethanol and dry.

  S3) Diffusion process: The Tb-plated layer magnet obtained from the ionic liquid plating process S2) is heat-treated at 925 ° C. for 5 hours under the condition that the absolute vacuum exceeds 0.01 Pa.

  S4) Aging treatment step: The magnet obtained from the diffusion step S3) is aged at 510 ° C. for 3 hours under the condition that the absolute vacuum exceeds 0.01 Pa. The obtained magnet was cut into a magnet having a size of 9 mm × 9 mm × 2 mm and measured, and the results obtained are shown in Table 3.

  For comparison, the sintered magnet obtained from the magnet manufacturing step S1) is not subjected to the ionic liquid plating step S2) and the diffusion step S3), but is directly subjected to the aging treatment step S4), and the dimension is 9 mm. A magnet having a size of 9 mm × 2 mm was processed and measured to obtain Comparative Example 3. See Table 3 for results.

Table 3

  As can be seen from Table 3, in Example 7-9, the residual magnetic flux density and the maximum magnetic energy product were slightly decreased as compared with Comparative Example 3, but the intrinsic coercivity was clearly increased. The plating temperature has an influence on all of the residual magnetic flux density, the maximum magnetic energy product, and the intrinsic coercive force of the magnet, and the influence on the intrinsic coercive force is most obvious.

  The present invention is not limited to the above-described embodiments, and various modifications, improvements, and alternatives that can be conceived by those skilled in the art are included in the scope of the present invention without departing from the spirit of the present invention.

Claims (10)

R-Fe-BM type sintered magnet (R is one or more selected from Nd, Pr, Dy, Tb, Ho, Gd, and the content of R is 24wt% to 35wt% of the total weight of the sintered magnet. M is one or more selected from Ti, V, Cr, Mn, Co, Ni, Ga, Ca, Cu, Zn, Si, Al, Mg, Zr, Nb, Hf, Ta, W, and Mo The content of M is 0-5 wt% of the total weight of the sintered magnet, the content of B is 0.5 wt% -1.5 wt% of the total weight of the sintered magnet, and the balance is Fe Magnet manufacturing process S1), which manufactures
An ionic liquid plating process in which a heavy rare earth metal is plated on the surface of the sintered magnet by an ionic liquid plating process to form a magnet with a plating layer, the sintered magnet having a thickness of 10 mm or less in at least one direction In the ionic liquid plating process, the plating solution contains an ionic liquid, a heavy rare earth salt, a Group VIII metal salt, an alkali metal salt, and an additive, the anode is a heavy rare earth metal or a heavy rare earth alloy, and the cathode is the firing electrode. Ionic liquid plating step S2), which is a magnet, has a plating temperature of 20-50 ° C., and a plating time of 15-80 min.
Diffusion step S3), wherein the magnet with plating layer is heat-treated to diffuse heavy rare earth metal into the sintered magnet, and
Aging treatment step S4) for aging treatment of the magnet obtained from the diffusion step S3)
A method for producing a permanent magnet material comprising:
The ionic liquid is a compound having the following structure:

(R ₁ and R ₂ are each independently selected from C ₁ -C 8 alkyl, and X is selected from Cl ⁻ , CF ₃ SO ₃ ^— or N (CN) ₂ ^— ).
The method for producing a permanent magnet material, wherein the additive is selected from ethylene glycol, urea, an aromatic compound, or an alkyl halide. R ₁ and R ₂ are each independently selected from C1-C4 alkyl, and X is selected from CF ₃ SO ₃ ^— or N (CN) ₂ ^—. Item 2. The method according to Item 1.   The ionic liquid is 1-butyl-3-methylimidazolium chloride, 1-butyl-3-ethylimidazolium chloride, 1,3-bismethylimidazolium chloride, 1-hexyl-3-methylimidazolium chloride, 1 chloride. -Octyl-3-methylimidazolium, 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-ethylimidazolium trifluoromethanesulfonate, 1,3-bismethylimidazolium trifluoromethanesulfone Acid salt, 1-hexyl-3-methylimidazolium trifluoromethanesulfonate, 1-octyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium dicyandiamide salt, 1-butyl-3 -Ethylimidazolium dicyandiamide salt, 1,3-bismethylimidazolium dicyandiamide salt, 1-hexyl-3-methyl The process according to claim 1, characterized in that it is selected from tilimidazolium dicyandiamide salt or 1-octyl-3-methylimidazolium dicyandiamide salt. In the plating solution, the heavy rare earth element of the heavy rare earth salt is selected from Gd, Tb, Dy or Ho, and the Group VIII metal of the Group VIII metal salt is selected from Fe, Co or Ni. The alkali metal of the alkali metal salt is selected from Li, Na or K, and the additive is an aromatic compound,
In the anode, the heavy rare earth metal is selected from Gd, Tb, Dy or Ho, and the heavy rare earth alloy is selected from an alloy formed of the heavy rare earth metal and Fe. The method of claim 1. In the plating solution, the heavy rare earth salt is a chloride, nitrate or sulfate of a heavy rare earth element, the Group VIII metal salt is a Group VIII metal chloride, and the alkali metal salt is an alkali metal chloride. And the aromatic compound is one or more selected from benzene, toluene, xylene, and ethylbenzene,
5. The method according to claim 4, wherein, in the anode, the heavy rare earth metal is Tb, and the heavy rare earth alloy is an alloy formed of Tb and Fe.   The ratio of the total amount of the heavy rare earth salt and the group VIII metal salt to the amount of the ionic liquid is 0.25 to 3: 1. The amount of the heavy rare earth salt and the group VIII metal salt The ratio of the amount is 0.25 to 10: 1, and in the plating solution, the concentration of the alkali metal salt is 10 to 200 g / L, and the volume ratio of the additive to the ionic liquid is 10 vol% to 400 vol%. The method of claim 1, wherein: 2. The method according to claim 1, wherein the ionic liquid plating step S <b> 2) is performed by employing one of the following methods under anhydrous and oxygen-free conditions.
(1) Constant current plating with current density of 5-20 mA / cm ² (2) Pulse voltage average value is 5-8V, duty ratio is 20% -50%, pulse frequency is 2-5kHz There is a pulse voltage plating.   The plating solution is obtained by uniformly mixing the heavy rare earth salt, the group VIII metal salt and the ionic liquid under anhydrous oxygen-free conditions at a temperature of 80 ° C. or less, and adding an alkali metal salt and an additive. The method according to claim 1, further comprising the step of preparing a plating solution to obtain   In the diffusion step S3), the heat treatment temperature is 850 to 1000 ° C. and the heat treatment time is 3 to 8 hours; in the aging treatment step S4), the treatment temperature is 400 to 650 ° C. and the treatment time is 2 The method according to claim 1, characterized in that it is ˜5 hours. The magnet manufacturing step S1)
Smelting process S1-1) to smelt magnet raw material and form an alloy sheet with a thickness of 0.01-2mm,
The alloy sheet is subjected to hydrogen storage / release treatment in a hydrogen crushing furnace to form a magnetic coarse powder having an average particle size D50 of 200 to 350 μm, and then the magnetic coarse powder is subjected to an average particle size D50 of 2 by a jet mill. Milling step S1-2) to crush to magnetic fine powder of ~ 20μm,
A molding step S1-3) in which the magnetic fine powder is pressed into a green body by the action of an orientation magnetic field; and
The green body is sintered and shaped at a sintering temperature of 960 to 1100 ° C., and then cut into a sintered magnet, and the sintered magnet has an oxygen content of less than 2000 ppm. Cutting process S1-4)
The method according to claim 9, comprising: